Bat Foraging in Tamarisk and Willow: A Survey of Species Richness along the Lower Owens River in California
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Invasion by tamarisk (Tamarix spp.) has contributed to a host of problems along riparian systems in the American southwest. This non-native invasive plant originally from Eurasia has been implicated with increased desertification and salination of the soil, greater fire danger, loss of habitat for native species, and in some cases decreased biodiversity (Dudley et al. 2000). Tamarisk has invaded the Lower Owens River of the Owens Valley in eastern California. The Lower Owens River Project is an endeavor to restore water to the Owens Valley that was previously appropriated by the Los Angeles Department of Water and Power and to restore a natural and healthy ecosystem riparian ecosystem. A substantial aspect of this project is the removal of tamarisk, but the role of tamarisk as part of ecosystems in the Lower Owens Valley is not yet well understood. This study, using bat as indicators of habitat health and productivity, examines the health of ecosystems dominated by tamarisk as compared with ecosystems dominated by native willow. Since bats forage using echolocation, I was able to identify specific species foraging in a habitat by recording and analyzing their calls. I based my hypothesis on previous studies, believing that if there were substantial differences in ecosystem health between tamarisk and willow dominated habitats, these differences would be reflected in the species richness measurements. The results of this investigation show that bats displayed little to no preference for either tamarisk or willow as potential foraging sites. There did appear to be a relationship however, between the species richness of the sites and their proximity to water. Results from studies of this nature are important for guiding natural resource management projects like the Lower Owens River Project. Further investigation, over a longer period of time, will be helpful in assessing the complex role tamarisk plays in Lower Owens River ecosystems.